MeO-biphep and binap ligands as six-electron donors to ruthenium(II). X-ray and NMR studies on Cp-, pyrrole-, and indole-derived complexes

Article abstract of DOI:10.1021/om9707275

Ru(II) complexes of the chiral ligands Binap and MeO-Biphep containing six-electron hydrocarbon donors, such as Cp, a deprotonated pyrrole, or the benzene ring of indole, attain the 18-electron configuration by complexing a proximate biaryl double bond. The solid-state structures for two of these, [RuCp(2)]BF₄ and [Ru(indole)(2)](BF₄)₂ (2 = (6,6′-dimethoxybiphenyl-2,2′-diyl)bis(bis(3,5-di-tert-butylphenyl) phosphine)), have been determined by X-ray diffraction. They reveal that a biaryl double bond, immediately adjacent to one P-donor, coordinates to the ruthenium, thus making the chelating ligand a six-electron donor. The double bonds remain coordinated in solution as shown by HMBC ¹³C,¹H long-range correlation spectroscopy. However, 2-D NMR exchange spectroscopy suggests that the biaryl double bond is weakly coordinated since the two halves of the C₂-symmetric Binap (or MeO-Biphep) ligands are in slow exchange at ambient temperature.

Full text of DOI:10.1021/om9707275

5756
Organometallics 1997, 16, 5756-5762
MeO-Bip h ep a n d Bin a p Liga n d s a s Six-Electr on Don or s
to Ru th en iu m (II). X-r a y a n d NMR Stu d ies on Cp -,
P yr r ole-, a n d In d ole-Der ived Com p lexes
Nantko Feiken, Paul S. Pregosin,* and Gerald Trabesinger
Laboratorium fu¨r Anorganische Chemie, ETH Zentrum, 8092 Zu¨rich, Switzerland
Alberto Albinati* and Giacomo L. Evoli
Chemical Pharmacy, University of Milan, I-20131 Milan, Italy
Received August 18, 1997X
Ru(II) complexes of the chiral ligands Binap and MeO-Biphep containing six-electron
hydrocarbon donors, such as Cp, a deprotonated pyrrole, or the benzene ring of indole, attain
the 18-electron configuration by complexing a proximate biaryl double bond. The solid-
state structures for two of these, [RuCp(2)]BF4 and [Ru(indole)(2)](BF4)2 (2 ) (6,6′-
dimethoxybiphenyl-2,2′-diyl)bis(bis(3,5-di-tert-butylphenyl)phosphine)), have been determined
by X-ray diffraction. They reveal that a biaryl double bond, immediately adjacent to one
P-donor, coordinates to the ruthenium, thus making the chelating ligand a six-electron donor.
The double bonds remain coordinated in solution as shown by HMBC 13C,1H long-range
correlation spectroscopy. However, 2-D NMR exchange spectroscopy suggests that the biaryl
double bond is weakly coordinated since the two halves of the C2-symmetric Binap (or MeO-
Biphep) ligands are in slow exchange at ambient temperature.
In tr od u ction
bonds, e.g., in the pentadienyl complex, 3. This bonding
New applications in organic synthesis involving chiral
bidentate phosphine complexes in connection with
enantioselective homogeneous catalysis now appear
regularly.1 Although there are many useful and com-
mercially available chiral ligands, the atropisomeric
class, which includes Binap2 (1) and MeO-Biphep3
(specifically 24,5), has proven immensely successful.
mode was somewhat unexpected, so that we have
considered additional Ru(II) complexes of both 1 and 2
to determine whether the bonding in 3 was an oddity
or whether this capability could be extended to a wider
variety of compounds. The 16-electron five-coordinate
hydrido cation [RuH(2)(isopropyl alcohol)2]+ does not
show this type of bonding.5 We report here on the Binap
complexes 4 and 5 as well as on the MeO-Biphep
complexes 6-8 (see Scheme 1), all of which show this
novel type of η4-coordination mode.
We have recently shown4 that Ru(II) complexes of 2
are capable of coordinating one of the biaryl double
X Abstract published in Advance ACS Abstracts, December 1, 1997.
(1) Organic Synthesis via Organometallics OSM 5; Helmchen, G.,
Dibo, J ., Flubacher, D., Wiese, B., Eds.; Vieweg: Braunschweig/
Wiesbaden, 1997. Trost, B. Angew. Chem. 1995, 107, 285. Hayashi, T.
In Catalytic Asymmetric Synthesis; Ojima, I., Ed.; VCH Publishers,
Inc.: New York, 1993; p 325. Brown, J . M.; Chem. Soc. Rev. 1993, 25.
(2) Kitamura, M.; Noyori, R. Mod. Synth. Meth. 1989, 5, 116. Ohta,
T.; Tonomura, Y.; Nozaki, K.; Takaya, H.; Mashima, K. Organometal-
lics 1996, 15, 1521. Zhang, X.; Uemura, T.; Matsumura, K.; Sayo, N.;
Kumobayashi, H.; Takaya, H. Synlett 1994, 501. Kitamura, M.;
Tokunaga, M.; Noyori, R. J . Am. Chem. Soc. 1993, 115, 144. Ohta, T.;
Miyake, T.; Seido, N.; Kumobayashi, H.; Akutagawa, S.; Takaya, H.
Tetrahedron Lett. 1992, 33, 635. Mashima, K.; Hino, T.; Takaya, H. J .
Chem. Soc., Dalton Trans. 1992, 2099. Ohta, T.; Takaya, H.; Noyori,
R. Inorg. Chem. 1988, 27, 566.
(3) Schmid, R.; Broger, E. A.; Cereghetti, M.; Crameri, Y.; Foricher,
J .; Lalonde, M.; Mueller, R. K.; Scalone, M.; Schoettel, G.; Zutter, U.
Pure Appl. Chem. 1996, 68, 131. Heiser, B.; Broger, E. A.; Crameri, Y.
Tetrahedron: Asymmetry 1991, 2, 51. Schmid, R.; Foricher, J .;
Cereghetti, M.; Schoenholzer, P. Helv. Chim. Acta 1991, 74, 370.
Mezzetti, A.; Tschumper, A.; Consiglio, G. J . Chem. Soc., Dalton Trans.
1995, 49. Mezzetti, A.; Costella, L.; Del Zotto, A.; Rigo, P.; Consiglio,
G. Gazz. Chim. Ital. 1993, 123, 155.
Resu lts a n d Discu ssion
Solid -Sta te Str u ctu r es. The solid-state structures
of the MeO-Biphep complexes 7 and 8 with coordinated
η5-Cp and η6-indole ligands, respectively, were deter-
mined by X-ray diffraction methods, and several views
for these complexes are shown in Figures 1 and 2. The
local coordination spheres of both complexes consist of
(4) (a) Feiken, N.; Pregosin, P. S.; Trabesinger, G. Organometallics
1997, 16, 537. (b) Organic Synthesis via Organometallics OSM 5;
Helmchen, G., Dibo, J ., Flubacher, D. Wiese, B. Eds.; Vieweg: Braun-
schweig/Wiesbaden, 1997; p 155.
(5) Currao, A.; Feiken, N.; Macchioni, A.; Nesper, R.; Pregosin P.
S.; Trabesinger, G. Helv. Chim. Acta 1996, 79, 1587.
S0276-7333(97)00727-9 CCC: $14.00 © 1997 American Chemical Society

MeO-Biphep and Binap Ligands
Organometallics, Vol. 16, No. 26, 1997 5757
Sch em e 1. Nu m ber in g System for th e Com p lexes
the chiral six-electron phosphine donor (two P atoms
and the aryl double bond) plus the Cp or indole
hydrocarbons. In compound 7, the usual η5-Cp coordi-
nation mode is found, with all five carbons ca. equidis-
tant from the ruthenium. In the dicationic indole
compound 8, the benzene ring of the indole is complexed.
Inspection of both structures reveals that the coordi-
nation of the aryl double bond is facilitated by a
distortion of the biaryl moiety. Normally, the two biaryl
rings would be ca. perpendicular and thus the angle
made by the two lines connecting C1 and C4 and C1′
and C4′ would be ca. 0°; however, in both complexes,
the biaryl bends such that the angle between these two
lines is ca. 20° in 7 and ca. 34° in 8, thus making the
the π-system of the coordinated double bond more
accessible to the metal.
F igu r e 1. (a) ORTEP plot for a part of the cationic Cp
complex 7. (b) View22 of the entire cation.
There is an obvious tilt of the plane of the coordinated
indole in 8 relative to the plane defined by the metal
and the two P donors (see Figure 2). This is sufficiently
marked such that the six aromatic carbons are not all
equally separated from the metal atom. The carbons
with the two shortest distances are indicated by the
arrows in 9.
Nevertheless, the Ru-C1 and Ru-C6 bond lengths
are relatively long and lie between ca. 2.31 and 2.38Å.
In the cationic hydrido-styrene complex [RuH-
(PhCHdCH2)(η6-cymene)(PPh3)]+, Faller and co-work-
ers6 find Ru-C separations for the styrene of 2.195(6)
and 2.216(6) Å. Similarly, for the cationic hydrido-
ethylene derivative [RuH(C2H4)(C6Me6)(PPh3)]+, Werner
and co-workers7 report Ru-C values of 2.168(10) and
2.194(9) Å for the complexed ethylene.
Obviously, this distortion could be steric in origin;
however, there are no close contacts between the various
organic fragments of the chiral phosphine and the
indole. Possibly, this dicationic complex is distorting
toward an η4 16-electron species, i.e., 10. This would
allow the five-membered ring to retain aromaticity.
Unfortunately, the large experimental uncertainties do
not allow an exact analysis of the various Ru-C
distances. DuBois and co-workers8 have found a similar
tilt of the coordinated indolyl ligand in [Ru(η6-2,3-
dimethylindolyl)(η6-cymene)](BPh4), in which the NH is
(6) Faller, J . W.; Chase, K. J . Organometallics 1995, 14, 1592.
(7) Kletzin, H.; Werner, H.; Serhadli, O.; Ziegler, M. L. Angew.
Chem. 1983, 95, 49.

5758 Organometallics, Vol. 16, No. 26, 1997
Feiken et al.
F igu r e 3. Comparison23 of the structures of 7 and 8
showing that the benzene ring of the complexed indole in
8 occupies almost the same position as the Cp ligand in 7.
Moreover, there is no longer a set of pseudo-axial and
pseudo-equatorial P-aryl ring substituents.
Ta ble 1. Bon d Len gth s (Å) a n d Bon d An gles (d eg)
for 7 a n d 8
L ) Cp, 7
L ) indole, 8
Ru-P1
2.317(4)
2.273(4)
2.38(1)
2.31(1)
2.19(2)
2.19(2)
2.21(1)
2.23(1)
2.23(1)
Ru-P1
2.315(7)
Ru-P2
Ru-P2
2.287(7)
2.34(3)
2.31(3)
2.36(4)
2.27(3)
2.15(3)
2.26(3)
2.41(3)
2.44(4)
Ru-C1
Ru-C6
Ru-C1L
Ru-C2L
Ru-C3L
Ru-C4L
Ru-C5L
Ru-C1
Ru-C6
Ru-C4L
Ru-C5L
Ru-C6L
Ru-C7L
Ru-C8L
Ru-C9L
P1-Ru-P2
P1-Ru-C1
P1-Ru-C6
Ru-P1-C6
Ru-P1-C22
Ru-P2-C6′
Ru-P2-C36
Ru-P2-C50
93.5(1)
72.3(4)
47.1(4)
66.2(5)
123.7(4)
107.0(5)
118.2(5)
117.0(5)
P1-Ru-P2
P1-Ru-C1
P1-Ru-C6
Ru-P1-C6
Ru-P1-C22
Ru-P2-C6′
Ru-P2-C36
Ru-P2-C50
91.0(3)
71.7(7)
44.0(6)
67.8(9)
122.7(9)
106.4(10)
113.4(9)
118.7(8)
occupy more pseudo-equatorial-like positions. From
Figure 3, one also sees that the coordinated benzene ring
of 8 occupies essentially the same space as the Cp ligand
in 7 and that there are no unexpected steric effects
disturbing the coordination of the the indole ligand.
F igu r e 2. (a) ORTEP plot for the dicationic indole complex
8. (b) View22 of the entire dication.
deprotonated. They have also reported9 the solid-state
structure for the dication [Ru(η6-1-Me-indoline)(η6-
cymene)](OTf)2.
The four Ru-P separations (ca 2.27-2.32 Å) as well
as the 12 P-C bond lengths (ca 1.77-1.86 Å) in 7 and
8 are relatively routine.11 The observed P-Ru-P bond
angles of 93.5(1)° and 91.0(3)°, respectively, suggest no
special strain and fall within the expected range for
MeO-Biphep complexes, e.g., [RuH(isopropyl alcohol)2-
(2)]+ ) 91.0(3)°,5 [RuH(p-cymene)(2)]+ ) 91.1(6)°,10 [Ru-
(η5-C8H11)(2)] ) 96.9(1)°.4a
Solu tion Stu d ies on th e Cp Com p lexes. Given
that the biaryl double bond coordination in this MeO-
Biphep series seems to have some generality, it was of
interest to compare the solution characteristics of
related Binap and Biphep derivatives. The solid-state
As a consequence of the coordination of the biaryl
double-bond in 7 and 8, one observes very different
angles about the two P atoms (see Table 1). For the
Ru-P1-C6 angles in these compounds, the values are
ca. 66° and 68°, respectively, due to the additional olefin
complexation. However, for Ru-P2-C6′, we find the
more routine values of ca. 107° and 106°, respectively.
It is interesting to compare the observed structures
of 2 in 7 and 8 (see Figure 3) with that found for 2 in
[RuH(p-cymene)(2)]+,10 which has a conventional MeO-
Biphep bidentate coordination mode. In the latter, we
observe the now classical pseudo-axial and pseudo-
equatorial arrangement of the P-phenyl groups; how-
ever, in 7 and 8, three of the P-phenyl groups now
(11) (a) DuBois, M. R.; Parker, K. G.; Ohman, C.; Noll, B. C.
Organometallics 1997, 16, 2325 (b) Gao, J .; Ikariya, T.; Noyori, R.
Organometallics 1996, 15, 1087. (c) Zanetti, N. C.; Spindler, F.;
Spencer, J .; Togni, A.; Rihs, G. Organometallics 1996, 15, 860. (d)
Mudalige, D. C.; Rettig, S. J .; J ames, B. R.; Cullen, W. R. J . Chem.
Soc., Chem. Commun. 1993, 830. (e) Cashman, R. S. M.; Butler, I. R.;
Cullen, W. R.; J ames, B. R.; Charland, B. J . P.; Simpson, J . Inorg.
Chem. 1992, 31, 5509.
(8) Chen, S.; Carperos, B.; Noll, B.; Swope, J .; Dubois, M. R.
Organometallics 1995, 14 1221.
(9) Chen, S.; Vasquez, L.; Noll, B. C.; Dubois, M. R. Organometallics
1997, 16, 175.
(10) Trabesinger, G.; Albinati, A.; Feiken, N.; Kunz, R. W.; Pregosin,
P. S.; Tschoerner, M. J . Am. Chem. Soc. 1997, 119, 6315.

MeO-Biphep and Binap Ligands
Organometallics, Vol. 16, No. 26, 1997 5759
Ta ble 2. Selected NMR Da ta a for Com p lexes 4-7
5b,e 6b,d
4c,e
7b,d
1H
13C
31P
1H
13C
31P
1H
13C
31P
1H
13C
31P
2
1
55.0
87.4
2
1
56.9
88.2
6
1
69.7
88.6
6
1
66.4
86.5
11
12
13
14
15
117.7
82.2
84.5
90.7
88.4
Cp
4.40
88.3
8
9
10
11
6.48
3.79
4.66
3.92
104.5
88.2
84.9
Cp
4.13
86.8
4.82
4.31
4.04
3.29
118.7
PA
PB
2J
5.2
75.0
44
PA
PB
2J
14.9
74.9
43.9
PA
PB
2J
8.2
81.9
45.8
PA
PB
2J
8.2
79.4
47.1
a
b
d
Chemical shifts in ppm, coupling constants in Hertz, CD2Cl2 solutions. 293 K. c 243 K. 400 MHz. e 500 MHz.
F igu r e 4. 31P spectrum for 4 revealing the low-frequency
shift of PA due to the η6-bonding mode of the Binap ligand
(CD2Cl2, 243 K, 500 MHz).
structure of [Ru(Cp)(Binap)]+, 5, is known,12 and samples
of this and the neomenthyl Cp-substituted analog, 4,
were available.13
The appropriate one- and two-dimensional NMR
spectra for these compounds, 4, 5, and 7, were obtained.
Figure 4 shows the 31P spectrum for the neomenthyl-
Cp derivative 4 and reveals an AX spin pattern (δ )
75.0 and 5.2, 2J (P,P) ) 44 Hz), with one of the two
phosphorus spins resonating at very low frequency (the
31P spectrum for the Cp derivative is qualitatively the
same, see Table 2). This unexpected low-frequency
resonance is now recognized4,12 to be typical of this η4-
bonding mode and can be assigned to the P donor
proximate to the coordinated olefin.
Figure 5 shows the long-range C,H correlation for the
cation [RuCp(Binap)]+. One finds cross peaks stemming
from the two- and three-bond J (C,H) coupling constants,
which pinpoint the positions of the very difficult to
observe 13C signals14 arising from the coordinated biaryl
double bond. The C2 resonance correlates to the protons
at C3 and C4; whereas the C1 signal shows cross peaks
from the protons of C3 and C8. In all three derivatives,
4, 5, and 7, these 13C resonances are shifted markedly
to low frequency, in keeping with the literature15 for a
coordinated double bond. For [RuCp(Binap)]+, the C1
resonance lies under the Cp signal. A summary of the
F igu r e 5. C,H long-range correlation for 5 showing the
cross peaks due to the two biaryl carbons which coordinate
to Ru(II) (CD2Cl2, 293 K, 400 MHz). For these complexes
it is normal that the biaryl carbons have long T1’s. C1 lies
under the Cp.
pertinent NMR data for these three complexes is also
given in Table 2. From both the solid- and solution-
state data, it is clear that the Binap and MeO-Biphep
ligands are capable of this type of biaryl double-bond
bonding in these Cp complexes.
Figure 6 shows the proton 2-D exchange spectrum16
for the cation [RuCp(Binap)]+. Analysis of the spectrum
shows that the two halves of the chiral auxiliary are
(12) Pathak, D. D.; Adams, H.; Bailey, N. A.; King, P. J .; White, C.
J . Organomet. Chem. 1994, 479, 237.
(13) We thank Dr. Colin White, University of Sheffield, for the
generous gift of these two Binap complexes.
(14) These fully substituted aromatic carbons have long spin-lattice
relaxation times. C1 does not even have a geminal proton to assist
the dipole-dipole relaxation. Consequently, we rarely observe this
resonance in the conventional 1-D 13C spectrum. Fortunately, the
intensity of the cross peaks in a 2-D C,H proton-detected correlation
depends on both the 13C and 1H magnetization, so that the appropriate
cross peaks are readily visible.
(16) For applications of 2-D exchange spectroscopy, see: Albinati,
A.; Eckert, J .; Pregosin, P. S.; Ruegger, H.; Salzmann, R.; Stoessel, C.
Organometallics 1997, 16, 579. Barbaro, P.; Currao, A.; Herrmann,
J .; Nesper, R.; Pregosin, P. S.; Salzmann, R. Organometallics 1996,
15, 1879. Barbaro, P.; Pregosin, P. S.; Salzmann, R.; Albinati, A.; Kunz,
R. W. Organometallics 1995, 14, 5160. Herrmann, J .; Pregosin, P. S.;
Salzmann, R.; Albinati, A. Organometallics 1995, 14, 3311. Pregosin,
P. S.; Salzmann, R.; Togni, A. Organometallics 1995, 14, 842. Breutel,
C.; Pregosin, P. S.; Salzmann, R.; Togni, A. J . Am. Chem Soc. 1994,
116, 4067. Magn. Reson. Chem. 1994, 32, 297. Lianza, F.; Macchioni,
A.; Pregosin, P. S.; Ru¨egger, H. Inorg. Chem. 1994, 33, 4999.
(15) Mann, B. E.; Taylor, B. F. 13C NMR Data for Organometallic
Compounds; Academic Press: London, 1981. Adams, C. M; Hafner,
A.; Koller, M.; Marcuzzi, A.; Prewo, R.; Solan, I.; Vincent, B.; von
Philipsborn, W. Helv. Chim. Acta 1989, 72, 1658.

5760 Organometallics, Vol. 16, No. 26, 1997
Feiken et al.
F igu r e 6. Aromatic section of the 1H-NOESY for the
Binap complex 5 showing the exchange between the two
halves of the C2-symmetric ligand (CD2Cl2, 293 K, 400
MHz).
F igu r e 7. ROESY (CD2Cl2, 243 K, 500 MHz) and NOESY
for 4 (CD2Cl2, 300 K, 500 MHz) showing the (+)-neomen-
thyl-Cp protons versus the aromatic protons. At 300 K
(bottom), all ortho protons for the R, â, γ, and δ rings show
interactions to all the Cp, reflecting the free rotation of (+)-
neomenthyl-Cp protons at 300 K. The broadended aro-
matic resonances is consistent with this rotation. At 243
K (top), the NOEs now reflect one well-defined position of
(+)-neomenthyl-Cp with respect to the BINAP ligand.
Protons 13 and 14 are broader due to slow rotation of the
(+)-neomenthyl moiety around the Ru-Cp axis.
exchanging (e.g., 3 with 3′ and 8 with 8′ are clearly
visible). These dynamics are consistent with the process
shown in the figure and confirm that the biaryl double
bond is not strongly bound to Ru (in keeping with the
crystallographic bond length data) and that the metal
can easily reach the 16-electron configuration by dis-
sociating the biaryl double bond. The neomenthyl
analog, 4, shows similar dynamic behavior. We have
demonstrated almost identical dynamics for the cationic
η5-pentadienyl complex [Ru(η5-C8H11)(2)]+, 3.4
Solu t ion St u d ies on t h e P yr r ole a n d In d ole
Com p lexes. The MeO-Biphep deprotonated pyrrole
derivative 6 shows NMR characteristics which are
similar to those for its Cp analog 7, see Table 2. The
biaryl double bond is coordinated (δ C1 ) 88.6 and δ
C6 ) 69.7), and the complex shows one of the two 31P
The neomenthyl-Cp complex 4 is interesting in that
it sheds some light on possible close contacts between
a bulky Cp substituent and the Binap phenyl groups.
1
The H NOESY spectrum for this complex at ambient
2
temperature (lower trace of Figure 7) shows random
contacts between the four Cp spins, 12-15, and the
Binap ortho P-phenyl protons, i.e., the Cp moiety
rotates fairly freely, thus allowing these protons to
periodically approach the different Binap sites. At 243
K (upper trace), the rotation is relatively slow and the
contacts to these same ortho P-phenyl protons, are
much more selective, e.g., H12 now shows relatively
strong NOEs to the o-R and o-δ protons, but H14 reveals
little or no NOE contacts to these Binap aryl protons.
Furthermore, the aliphatic methine proton, immediately
adjacent to the Cp ring (not shown in the figure), shows
only one strong contact to the ortho protons of the R
ring. These NOE data suggest that in a hypothetical
enantioselective reaction involving this neomenthyl Cp
ligand, the transfer of chiral information from Binap
would be more efficient at low temperature.
signals at low frequency (δ ) 81.9 and 8.2, J (P,P) )
45.8 Hz). Interestingly, the four 13C signals from the
deprotonated pyrrole, C8-C11, are all different: δ )
104.5, 88.2, 84.9, and 118.7, respectively. In uncom-
plexed pyrrole, the C2 and C3 carbons resonate at δ ca.
117.3 and 107.6 ppm, respectively. Although the free
ligand is a poor model for 6, there are recent studies on
η5-pyrrolyl11a and η5-methyl-substituted pyrrolyl17 Ru
complexes. For RuH(η5-pyrrolyl)(PPh3)2 and RuI(η5-
pyrrolyl)(PPh3)2, one observes 13C signals at 110.0, 82.0
and 107.4, 84.3 ppm, respectively, for the R and â
pyrrolyl carbons in these complexes.11a Consequently, the
observed difference between the two 13C signals adjacent
to nitrogen in 6 (104.5 and 118.7 ppm) is somewhat of
a surprise. Assuming the now established η5 -bonding
mode11a,17 for this fairly small ligand, one would not
expect marked steric effects. Perhaps the η5-pyrrolyl

MeO-Biphep and Binap Ligands
Organometallics, Vol. 16, No. 26, 1997 5761
is leaning toward an η3 mode, i.e., as shown in 11;
however, without an accurate solid-state structure, this
is rather speculative.
Ta ble 3. Exp er im en ta l Da ta for th e X-r a y Stu d y
of 7 a n d 8
compound
7
8
formula
mol wt
data collection T, K
cryst syst
space group
a, Å
C75H110BF4O2P2Ru
1284.46
200
othorhombic
P212121
14.577 (9)
18.846 (8)
28.433 (10)
7811 (7)
4
C78H102B2F8NO2P2Ru
1422.43
190
orthorhombic
P212121
15.622 (9)
18.216 (6)
28.616 (8)
8143 (8)
4
b, Å
c, Å
V, Å3
Z
F(calcd), g cm-3
1.092
2.827
Mo KR
1.160
2.838
In solution, the indole compound 8 shows at least
three different complexes so that a detailed analysis of
its solution properties was not undertaken. 31P NMR
suggests that two of these have the η4-bonding mode.
Most probably, these two η4-compounds differ in the
position of the indole five-membered ring with respect
to the η4-Biphep ligand. The third complex shows a very
broad doublet at ca. 67 ppm and has not been identified.
We also know from a natural abundance HMQC 15N
spectrum that all three species retain the N-H bond
based on their very similar 15N chemical shifts. Nev-
ertheless, the complexity of the 1H NMR spectrum
resulting from this mixture prohibits further structural
discussion.
In summary, the bidentate ligands in complexes 4-8,
all reveal the η4 six-electron-donor bonding mode.
Obviously, there is nothing special in the tert-butyl
MeO-Biphep ligand 2 since Binap readily produces the
same type of bonding. Both 5 and 7 have similar
dynamics in solution, confirming that the Ru(II) center
should be able to take up new ligands by disssociating
the biaryl double bond.
µ, cm-1
radiation
(graphite monochromated λ ) 0.710 69 Å)
2.5 < θ < 24.0
6053
θ range, deg
no. of indep data coll
2.5 < θ < 22.7
6058
no. of obsd. reflns (no) 3951
(|Fo| > 3.5σ(|F|))
2669
transmission coeff
0.5688-1.5402
n.a.
Ra
Rw
GOF
0.065
0.086
2.291
0.083
0.106
2.495
a
a
2
R ) ∑(|Fo - (1/k)Fc|)/∑|Fo|; Rw ) [∑w(Fo - (1/k)Fc)2/∑w|Fo| ]1/2
where w ) [σ2(Fo)]-1; σ(Fo) ) [σ2(Fo2) + f 4(Fo2)]1/2/2Fo.
The structures were solved by a combination of Patterson
and Fourier methods and refined by full-matrix least-squares18
(the function minimized being ∑[w(Fo - 1/kFc)2]). No extinction
correction was deemed necessary. The scattering factors used,
corrected for the real and imaginary parts of the anomalous
dispersion, were taken from the literature.19
The contribution of the hydrogen atoms in calculated
positions (C-H ) 0.95 Å, B(H) ) 1.3B(Cbonded) (Å2)) was taken
into account but not refined. Upon convergence (see Support-
ing Information Table S1), no significant features were found
in the Fourier difference maps of both compounds. The
handedness of the structures were tested by refining both
enantiomorphs; the coordinates giving the significantly20 lower
Rw factors were used. Final agreement factors and other
relevant data for the refinement are given in Table 3. All
calculations were carried out using the Enraf-Nonius MOLEN
package.18
Exp er im en ta l Section
Gen er a l. All reactions were performed in an atmosphere
of Ar using standard Schlenk techniques. Dry and oxygen-
free solvents were used. Ru(OAc)2 2 was provided by F.
1
Hoffman-La Roche, Basel. Routine H (300.13 MHz) and 31P
Str u ctu r a l Stu d y of 7. An empirical absorption correc-
tion21 was applied to the data set by using azimuthal (Ψ) scans
of three “high-ø” (ø > 82°) reflections. Of the 6053 independent
data collected, 3951 were considered as observed and used for
the refinement. The final full-matrix least-squares refinement
cycles were carried out using anisotropic displacement param-
eters for the ruthenium, phosphorous, and fluorine atoms and
for the atoms of the cyclopentadienyl and MeO moieties. All
other atoms were treated isotropically: increasing the number
of refined parameters, did not yield a significantly better
model.20
Str u ctu r a l Stu d y of 8. As mentioned above, only crystals
of very unsatisfactory quality could be obtained and used for
the data collection, resulting in a poor quality of the structure
determination (cf. the limited number of observed reflections
and the high values of the esd’s of the refined parameters). A
total of 6058 independent reflections were collected of which
only 2669 were observed (Fo > 3.5σ(F)) and used for the
refinement.
(121.5 MHz) NMR spectra were recorded with a Bruker DPX-
300 spectrometer. 19F (188.3 MHz) NMR spectra were re-
corded with a Bruker AC200 spectrometer. The two-dimen-
sional studies were carried out at using either 400 or 500 MHz
for 1H. Chemical shifts are given in ppm, and coupling
constants (J ) are given in Hertz. IR spectra were recorded
with a Perkin-Elmer 882 infrared spectrophotometer. El-
emental analyses and mass spectroscopic studies were per-
formed by the ETHZ analytical facility.
Cr ysta llogr a p h y. Crystals of 7 and 8 suitable for X-ray
diffraction were obtained from THF/hexane. For 8, it was only
possible to obtain crystals of poor quality and diffracting power.
Crystals of both compounds, mounted on glass fibers, were
cooled to 200 and 190 K, respectively, by using an Enraf-
Nonius FR558SH nitrogen gas-stream cryostat installed on the
CAD4 diffractometer, which was used for the space group
determination and for the data collection. Unit cell dimensions
were obtained by least-squares fit of the 2θ values of 25 high-
order reflections. Crystallographic and other relevant data are
listed in Table 3 and Supporting Information Table S1. Data
were measured with variable scan speed to ensure constant
statistical precision on the collected intensities. Three stan-
dard reflections were used to check the stability of the crystals
and of the experimental conditions and were measured every
hour. The collected intensities were corrected for Lorentz and
polarization factors.18
(18) MolEN: Molecular Structure Solution Procedere; Enraf-Non-
ius: Delft, The Netherlands, 1990.
(19) North, A. C. T.; Philips, D. C.; Mathews, F. S. Acta Crystallogr.
1968, A24, 351.
(20) Hamilton, W. C. Acta Crystallogr. 1965, 17, 502.
(21) International Tables for X-ray Crystallography; Kynoch Press:
Birningham, England, 1974; Vol. IV.
(22) WEB LAB VIEWER, version 1.1; Molecular Simulation Inc.,
1996.
(17) Kvietok, F.; Carperos, A. V.; DuBois, M. R. Organometallics
1994, 13, 60.
(23) ALCHEMY III. 3D Molecular Modelling Software; Tripos
Associates, Inc.: St. Louis, MS, 1992.

5762 Organometallics, Vol. 16, No. 26, 1997
Feiken et al.
One of the two tetrafluoroborate anions was found to be
highly disordered; therefore, a model was constructed using
the strongest peaks of a Fourier difference map. During the
refinement, the positional parameters of the fluorine atoms
were kept fixed and only their isotropic displacement param-
eters were allowed to vary. The structure was refined as
described above, using anisotropic displacement parameters
for the ruthenium, phosphorous, and oxygen atoms; all other
atoms were treated isotropically. No significant improvement
in the model20 was obtained by increasing the number of
refined parameters.
Syn th esis of 6. To a solution of Ru(OAc)22 (55.1 mg, 0.0441
mmol) in 5 mL of CH2Cl2 was added 10 equiv of pyrrole (30.6
µL, 0.44 mmol). After 5 min, 2.1 equiv of HBF4‚Et2O (0.093
mmol, 12.6 µL of a 7.3 M solution in diethyl ether) was added.
After 3 h, the reaction mixture was evaporated to dryness,
washed twice with 3 mL of hexane, and then redissolved in 5
mL of CH2Cl2. After washing with water (3 × 4 mL) and
drying over MgSO4, the solution was filtered through Celite
and evaporated to dryness. Washing with 2 mL of hexane and
drying in vacuo gave 42 mg (74%) of an orange powder. Anal.
Calcd for C74H101BF4NO2P2Ru: C, 69.12; H, 7.84. Found: C,
68.20; H, 8.15. MS (FAB): found 1198.7 (M+), calcd 1198.7.
IR (KBr): 1123-1040 cm-1 (BF4-; s, br). 31P{1H} NMR (CD2-
Cl2, 298 K): δ 81.9 (d, 46 Hz), 8.2 (d, 46). 19F{1H} NMR (CD2-
Cl2, 298 K): δ -153.6 (s, 25%, 10B, BF4-), -153.7 (s, 75%, 11B,
BF4-).
Syn th esis of 7. To a solution of Ru(OAc)22 (46.1 mg, 0.0369
mmol) in 2 mL of CH2Cl2 was added an excess of CpH (40 µL)
and then 2.05 equiv of HBF4‚Et2O (0.076 mmol, 10 µL of a
7.3 M solution in diethyl ether). After 3 h, the reaction mixture
was evaporated to dryness, washed twice with 4 mL of hexane,
and then redisolved in 4 mL of CH2Cl2. After washing with
water (3 × 4 mL) and drying over MgSO4, the solution was
filtered through Celite and evaporated to dryness. Washing
with 2 mL of hexane and drying in vacuo afforded 46 mg (97%)
of an orange powder. Anal. Calcd for C75H101BF4O2P2Ru: C,
70.13; H, 7.93. Found: C, 70.55; H, 8.45. MS (FAB): found
1197.7 (M+), calcd 1197.7. IR (KBr): 1182 cm-1 (BF4-; s, br).
31P{1H} NMR (CD2Cl2, 298 K): δ 79.4 (d, 47), 8.2 ppm (d, 47).
19F{1H} NMR (CD2Cl2, 298 K): δ -153.8 (s, 25%, 10B, BF4-),
-153.9 (s, 75%, 11B, BF4-).
Syn th esis of 8. To a solution of Ru(OAc)22 (62.3 mg, 0.0498
mmol) in 2 mL of CH2Cl2 was added an excess of indole (20
mg, 3.4 equiv, 0.17 mmol) and then 2.05 equiv of HBF4‚Et2O
(0.10 mmol, 14 µL of a 7.3 M solution in diethyl ether). After
3 h, the reaction mixture was evaporated to dryness, washed
twice with 3 mL of hexane, and then redisolved in 4 mL of
CH2Cl2. After washing with water (3 × 4 mL) and drying over
MgSO4, the solution was filtered over Celite and evaporated
to dryness. Washing with 2 mL of hexane and drying in vacuo
afforded 67 mg (92%) of a red powder. The compound could
be recrystallized by slow diffusion of hexane into a concen-
trated CH2Cl2 solution at -20 °C. Anal. Calcd for
C
78H103B2F8NO2P2Ru: C, 65.82; H, 7.29; N, 0.98. Found: C,
65.53; H, 7.41; 1.07. MS (FAB): found 1250.7 (M+), calcd
1248.8. 31P NMR: component A ) 75.4 (d, 46.3 Hz), 7.6 (d,
46.3 Hz); component B ) 75.0 (d, 48.4 Hz), 12.8 (d, 48.4 Hz);
component C is a very broad doublet centered at ca. 67 ppm
and is apparently involved in some form of exchange. Com-
ponents A and B are thought to be η4-complexes. The observed
15N chemical shifts are all in the relatively narrow region from
-250 to -256 ppm (CH3NO2).
Ack n ow led gm en t. P.S.P. thanks the Swiss Na-
tional Science Foundation, the ETH Zurich, and F.
Hoffmann-La Roche AG for financial support. A.A.
thanks the Italian CNR for support. We also thank F.
Hoffmann-La Roche AG for a gift of Biphep ligands and
the complex Ru(OAc)2(2), as well as J ohnson Matthey
for the loan of precious metals. Special thanks are due
to Dr. Heinz Ru¨egger for the 15N NMR and Dr. Dario
Drommi for experimental assistance.
Su p p or tin g In for m a tion Ava ila ble: Text giving experi-
mental details, tables for 7 and 8 as their BF4 salts of
positional and isotropic equivalent displacement parameters,
calculated positions of the hydrogen atoms, anisotropic dis-
placement parameters, and bond distances and angles, and
ORTEP figures showing the entire molecules and the full
numbering schemes for 7 and 8 as the BF4 salt (21 pages).
See any current masthead page for ordering information.
OM9707275